1. Field of the Invention
The present invention relates to a ΔΣ modulator.
2. Description of the Related Art
In the related art, a ΔΣ modulator applied to an A/D converter or so is known. The ΔΣ modulator converts an input analog quantity into a digital value and outputs it (for example, see Non-Patent Reference No. 1, i.e., “Feng Chen, Srinath Ramaswamy, Bertan Bakkaloglu, “A 1.5V 1 mA 80 dB Passive ΔΣ ADC in 0.13 μm Digital CMOS Process”, ISSCC 2003”). Generally speaking, in order to acquire high resolution in an A/D converter, a ΔΣ modulator of a second order or more, i.e., a ΔΣ modulator having two or more stages of integrators connected in a cascade manner, is used. As an integrator in a ΔΣ modulator, there is an integrator using a capacitor without using an operational amplifier (hereinafter, referred to as a “passive integrator”) other than an integrator that is an analog circuit including an amplifier circuit such as an operational amplifier (hereinafter, referred to as an “active integrator”). A ΔΣ modulator shown in the above-mentioned Non-Patent Reference No. 1 includes a plurality of passive integrators connected in a cascade manner.